What Muscle Is Used to Do Situps?

Targeted Muscle

Your rectus abdominis is one of four major muscles making up your abdominal muscle group. Yet, because it is the muscle responsible for "six-pack" abs, this is the most famous abdominal muscle. This muscle starts at the crest of your pubic bone and stretches horizontally up to your ribcage. It connects into your fifth, sixth and seventh ribs. Anytime you tilt your pelvis or flex your spine, your rectus abdominis is doing the majority of the work.

Supporting Muscles

While your rectus abdominis reaps the main benefits of a situp, nearly half a dozen other muscles are brought in to make this exercise possible. Your obliques, also part of the abdominal group, assist with flexing your spine. When you perform a situp, you bend your hip joint. Your iliopsoas, tensor fasciae latae, rectus femoris (part of your quadriceps) and sartorius muscles engage to assist with this motion. Your sartorius also helps with bending your knee joint, while your rectus femoris engages when straightening your knee joint.

Stabilizing Muscles

While your lower legs aren’t moving much during a situp, that doesn’t mean that muscles aren’t working. Your tibialis anterior, which runs from the top of your tibia, or shinbone, and connects to your big toe bone, is responsible for flexing your ankle. As you raise and lower during a situp, this joint flexes and extends.

Correct Form

Over the years, there have been different variations of the situp, all claiming to be the best. According to “Applied Physiology, Physiology, Nutrition and Metabolism” in 2008, the Canadian Society of Exercise Physiology partial situp produced the highest activation of abdominal muscles. For this situp, lie on your back face up and keep your arms by your sides with your palms facing the mat. Bend your knees so that your heels are in contact with the mat, but do not anchor your feet. Engage your abs and curl up while extending your fingers forward about 4 inches. Curl back down to the starting position and repeat.